I am trying to georeference a largish aerial image (50MB) to some GIS data I have and import it as a background. However the image imports extremely small - so small I cant see it!

I am using QGIS and the Georeferencer plugin. I select about 7 control points randomly across the image and I am using the thin plate spline with nearest neighbour resampling. The error is 0.00768. I have tried several transformation settings and set the target CRS to the project CRS, but get similar results.The control points appear in QGIS in the right positions.

Sorry Nathan, but as I am a new user, I cannot upload images yet.
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boberdorfMay 8 '12 at 3:37

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@boberdorf you can upload images TO and then share links FROM imgur.com
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SimbamanguMay 8 '12 at 5:37

@boberdorf Start a new project, set the SRS to World Mercator (just for testing), try polynomial 1 and 2 set the target SRS also to World Mercartor (SRID 3395) and come back with the results.
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PabloMay 8 '12 at 11:14

Hi Pablo, I recieved the similiar results using the method you noted. I tried numerous options to see what would happen, and even tried a different image (lower resolution) but that didnt work. Thanks for the advice
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boberdorfMay 9 '12 at 12:04

1 Answer
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If I understand you, tou want to use an aerial photograph to digitize something or as a background for data.
I do not think you can georeference an Aerial photograph with QGis georeferencer. That plug-in works for images with a constant scale. In an Aerial photograph you do not have a constant scale, since this one is related to the flying height and the focal length of the camera used. Flying height varies according the terrain´s topography. Nevertheless, you can try using grass i.ortho.photo procedure. In my experience it does work when Grass is installed in a linux environment. You can not use it in a Windows OS and I do not have Mac experience. Check this out